1. Field of the Invention
The present invention relates to an outboard motor (hybrid outboard motor) having a power unit (hybrid engine) including an internal combustion engine and a motor generator (serving both as an electric motor and a generator).
2. Description of the Related Art
Major types of propulsion unit or propulsion system for craft or boat include outboard motor, inboard-outdrive motor, inboard motor, and the like. The outboard motor, also called outboard drive or the like as illustrated in FIG. 31A, is integrally made up of an engine, auxiliary machines, gears and shafts of a drive system, a screw, and so on, and is mounted onto a transom board 2 of the stern of a hull 1. Typically mounted on a small boat or the like, the outboard motor can change in direction about an axis (steering function), and is also structured to be capable of being flipped up to avoid collision against an obstacle or the like while traveling (tilting function).
Further, the inboard-outdrive motor, also called inboard engine/outboard drive or the like as an installation method for a propulsion unit of a small craft or the like as illustrated in FIG. 31B, has an engine mounted in an inboard stern portion and a drive unit made up integrally of reduction gears, a forward and reverse clutch, a propeller, and so on and disposed on the exterior of the transom board 2.
Furthermore, the inboard motor is one of installation methods typically for a propulsion unit of a small craft or the like, as illustrated in FIG. 31C. Also called inboard drive, it is a method placing an engine, reduction gears, and a forward and reverse clutch in an inboard central portion or the like, extending a propeller shaft toward the stern, and placing the propeller under water from a craft bottom. A rudder determining the traveling direction of the boat is often placed behind the propeller. The engine is often a four-stroke diesel engine. Cooling methods for the engine include a direct water cooling method directly circulating water from the water area where the boat is used in a cylinder block and an indirect cooling method circulating clear water in the cylinder block, which is cooled in a heat exchanger by water from the water area where the boat is used, and the like.
Further, there is also known an electric motor-driven type outboard motor using an electric motor as a power source, which is structured integrally with auxiliary machines, gears and shafts of a drive system, a screw, and so on, to be mounted on a transom board of the stern of a hull.
Moreover, as described in Japanese Laid-open Patent Publication No. 2006-36086 or Japanese Laid-open Patent Publication No. 2008-137646, there is what is called a hybrid outboard motor, including an engine and an electric motor as a drive source for a propeller. The hybrid outboard motor described in Japanese Laid-open Patent Publication No. 2006-36086 or Japanese Laid-open Patent Publication No. 2008-137646 has an engine placed to have a crank shaft arranged along an upward and downward direction, and an electric motor disposed below this engine.
Particularly regarding the outboard motor, problems of conventional arts are considered. First, it is mounted in a form covering the stern (transom board), and thus the vicinity of the stern becomes a dead space, that is, it has a practical problem of not allowing boarding/getting off or the like using this space. Further, the outboard motor mounted onto the stern becomes an obstacle. Thus, a net, a caught fish or the like cannot be taking in via the stern.
Further, it is formed of a body completely separated from the boat hull, and it is quite difficult to match colors and shapes in the design of the hull and the design of the outboard motor.
Here, problems in packaging of conventional outboard motors are considered in relation with the inboard motor or the inboard-outdrive motor as other packaging methods.
The inboard motor has a propeller shaft, a propeller, a rudder, and the like projecting from the boat bottom which generate large fluid resistance, resulting in poor cruising performance and fuel efficiency. With the inboard motor in which the propeller shaft, the propeller, the rudder, and the like project from the boat bottom, it is not possible to cruise in a shallow sea area. When collided against a floating object on the water, the inboard motor can be damaged to a great extent because no shock absorbing mechanism is provided in itself. Incidentally, the same applies to those inboard motors having a latest propulsion unit called POD.
In both the inboard motor and the inboard-outdrive motor, since an engine is disposed in the hull and a propulsion unit is disposed on the exterior of the hull, it is laborsome to fit the engine in a small closed space, match axial centers of the engine and the propulsion unit, watertight sealing of a coupling portion of the engine and the propulsion unit, or the like. Further, since the engine is located inside the hull or in a deep position in the hull, maintenance is also laborsome.
The inboard-outdrive motor, since it is provided with a tilt mechanism, has a shock absorbing ability, but the tilt axis fulcrum is provided only in the vicinity of a drive shaft coupling the engine and the propulsion unit. Thus, the height of the gear case when tilted at a maximum position is low, and it is practically difficult to be pulled up above the water. Further, since the drive shaft is bent by a universal joint or the like, the tilt angle is small. Accordingly, when kept on the water, the propulsion unit cannot be in a dry state, and it is difficult to corrosion resistance. Further, in the inboard-outdrive motor, steering is performed by bending the drive shaft with a universal joint or the like. Thus, the motor has a small steering angle which results in poor turning performance.
In the inboard-outdrive motor, the engine drive shaft and the propulsion unit drive shaft are mechanically coupled, and thus relative positions of them are limited. Therefore, adjustment to an optimum propelling axis (propeller) position, which is determined by a boat shape, an operating condition, and the like, is not possible.
Further, since the engine drive shaft and the propulsion unit drive shaft are mechanically coupled in the inboard-outdrive motor, relative positions of them vary. Accordingly, the drive shaft coupling them and an exhaust passage are each covered by a bellows-shaped rubber tube to have a watertight structure. Such a tube needs to have plasticity, heat resistance, and weather resistance at the same time which are contradicting requirements, and thus often has a water leak. Thus, regular replacement of parts is required.
Next, fuel efficiency of the conventional outboard motor is considered in relation with a hybrid structure.
When a motor is placed right below a vertical axis engine (in the upward and downward direction) as a characteristic of the outboard motor (parallel hybrid system), the motor is sandwiched by the engine and an oil pan, and this lowers oil dripping performance of the engine. Further, the motor obstructs an exhaust passage of the engine, a cooling water passage of the engine, and a lubricating oil passage of the engine, posing difficulties in engine cooling, lubrication, and exhaust processing. Moreover, since the motor is surrounded by the engine, engine exhaust, and heat of the oil pan, it is difficult to cool the motor, and thus performance of the motor cannot be increased. Unspring weight increases and thus a steering driving force, a shock absorbing device, an engine suspension device, and an engine vibration damping device become large, resulting in increase in all of the size, weight and cost as the whole.
When the engine and the motor are placed in a gear case, in the parallel hybrid system the gear case becomes large, which increases its fluid resistance and worsens cruising performance and fuel efficiency. Unspring weight and the inertial mass around the tilt axis increase and thus a steering driving force, a shock absorbing device, an engine suspension device, and an engine vibration damping device become large, leading to increase in size, weight, and cost as the whole.
Further, when the engine is placed at a position as is conventional and the motor is placed in the gear case (parallel hybrid system), the gear case becomes large since the motor is located in the gear case, which increases its fluid resistance and worsens cruising performance and fuel efficiency. When a speed reducer is provided between the motor and the propeller to optimize efficiency of each of them, the gear case further becomes large, which further worsens cruising performance and fuel efficiency. Further, since there is a large distance between the motor and the engine, a delay and/or a mechanical loss occur when restart of the engine is performed by the driving motor accompanying stopping of idling, which is a fuel efficiency improving feature of the hybrid system. Unspring weight and the inertial mass around the tilt axis increase and thus a steering driving force, a shock absorbing device, an engine suspension device, and an engine vibration damping device become large, leading to increase in size, weight, and cost as the whole.
When the engine is placed at a position as is conventional, a generator is placed right below the engine, and the motor is placed in a gear case (series hybrid system), the generator is sandwiched by the engine and an oil pan, and this lowers oil dripping performance of the engine. Further, the generator obstructs an exhaust passage of the engine, a cooling water passage of the engine, and a lubricating oil passage of the engine, posing difficulties in engine cooling, lubrication, and exhaust processing. Moreover, since the generator is surrounded by the engine, engine exhaust, and heat of the oil pan, it is difficult to cool the generator, and thus performance of the generator cannot be increased. Since the motor is located in the gear case, the gear case becomes large, which increases its fluid resistance and worsens cruising performance and fuel efficiency.
When a speed reducer is provided between the motor and the propeller to optimize efficiency of each of them, the gear case further becomes large, which further worsens cruising performance and fuel efficiency. Unspring weight and the inertial mass around the tilt axis increase significantly and thus a steering driving force, a shock absorbing device, an engine suspension device, and an engine vibration damping device become large, leading to increase in size, weight, and cost as the whole.
Further, the case of adding an engine generator to a conventional pure electric outboard motor (series hybrid system) is considered.
The pure electric outboard motor has a small battery capacity and generally has a short cruising distance. When an engine generator is placed in a separate location (for example in a hull) to solve this, energy loss is large when current flows in and out of a battery (or an equivalent energy storage device), yielding quite low efficiency such that the total efficiency of generator, battery, and motor=generator efficiency×battery charging efficiency×battery discharging efficiency×motor efficiency.
Particularly, it has not been easy to transmit motive power of a power source appropriately and efficiency in a limited space in relation to achieving compactness, high performance, and the like.
Further, it has not been easy to tilt or steer smoothly and effectively in a limited space in relation to achieving compactness, high performance, and the like.